The present invention relates to a circuit for transforming a trigger signal into a pulse signal which has a predetermined constant pulse width.
For obtaining a direct-current voltage from an input signal, the input signal is conventionally transformed into a rectangular pulse by monostable multivibrator, and then the direct current voltage is generated from the rectangular pulse. The conventional monostable multivibrator is constructed of a pair of transistors the bases of which are respectively cross-connected to the collectors of the different transistors via an RC circuit. The pulse width of the output rectangular pulse depends on the time constant of the an RC circuit, the voltage of power supply and the base-emitter voltages and the collector-emitter saturation voltages of the transistors. The temperature fluctuation of the base-emitter voltage and the collector-emitter saturation voltage and variation of the power supply voltage cause considerable variation of the pulse width. Therefore the conventional monostable multivibrator is not suitable as a signal detector or frequency controller when a directcurrent voltage to be precisely respondent to the frequency of the input signal is needed.
Further, the conventional monostable multivibrator consumes large power, because either one or the other of the two transistors always allows the current to flow.